To produce an electronic book which is capable of displaying text data and playbacking voice data in a state where the both data are corresponded to each other, the text data and the voice data must be synchronously processed.
Usually, the text data are shown on a display and the voice data are outputted from a speaker, and the both data are manually synchronized. Therefore, a working efficiency of synchronously processing the text data and the voice data is very low, so it is difficult to generalize accessible electronic books.
These days, a technology for automatically synchronously processing text data and voice data has been proposed (see Patent Document 1).